Revert "[translate] Add translate ranker model loader."

components/translate/core/browser/translate_ranker.cc

Index: components/translate/core/browser/translate_ranker.cc
diff --git a/components/translate/core/browser/translate_ranker.cc b/components/translate/core/browser/translate_ranker.cc
new file mode 100644
index 0000000000000000000000000000000000000000..1341652f64293c9037dce916c4e903456a084ed5
--- /dev/null
+++ b/components/translate/core/browser/translate_ranker.cc
@@ -0,0 +1,311 @@
+// Copyright 2016 The Chromium Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+#include "components/translate/core/browser/translate_ranker.h"
+
+#include <cmath>
+
+#include "base/bind.h"
+#include "base/bind_helpers.h"
+#include "base/command_line.h"
+#include "base/metrics/histogram_macros.h"
+#include "base/profiler/scoped_tracker.h"
+#include "base/strings/string_util.h"
+#include "components/metrics/proto/translate_event.pb.h"
+#include "components/translate/core/browser/proto/translate_ranker_model.pb.h"
+#include "components/translate/core/browser/translate_download_manager.h"
+#include "components/translate/core/browser/translate_prefs.h"
+#include "components/translate/core/browser/translate_url_fetcher.h"
+#include "components/translate/core/common/translate_switches.h"
+
+namespace translate {
+
+namespace {
+
+typedef google::protobuf::Map<std::string, float> WeightMap;
+
+const double kTranslationOfferThreshold = 0.5;
+
+// Parameters for model fetching.
+const char kTranslateRankerModelURL[] =
+    "https://chromium-i18n.appspot.com/ssl-translate-ranker-model";
+const int kMaxRetryOn5xx = 3;
+const int kDownloadRefractoryPeriodMin = 15;
+const char kUnknown[] = "UNKNOWN";
+
+// Enumeration denoting the outcome of an attempt to download the translate
+// ranker model. This must be kept in sync with the TranslateRankerModelStatus
+// enum in histograms.xml
+enum ModelStatus {
+  MODEL_STATUS_OK = 0,
+  MODEL_STATUS_DOWNLOAD_THROTTLED = 1,
+  MODEL_STATUS_DOWNLOAD_FAILED = 2,
+  MODEL_STATUS_PARSE_FAILED = 3,
+  MODEL_STATUS_VALIDATION_FAILED = 4,
+  // Insert new values above this line.
+  MODEL_STATUS_MAX
+};
+
+double Sigmoid(double x) {
+  return 1.0 / (1.0 + exp(-x));
+}
+
+double ScoreComponent(const WeightMap& weights, const std::string& key) {
+  WeightMap::const_iterator i = weights.find(base::ToLowerASCII(key));
+  if (i == weights.end())
+    i = weights.find(kUnknown);
+  return i == weights.end() ? 0.0 : i->second;
+}
+
+GURL GetTranslateRankerURL() {
+  base::CommandLine* command_line = base::CommandLine::ForCurrentProcess();
+  return GURL(command_line->HasSwitch(switches::kTranslateRankerModelURL)
+                  ? command_line->GetSwitchValueASCII(
+                        switches::kTranslateRankerModelURL)
+                  : kTranslateRankerModelURL);
+}
+
+void ReportModelStatus(ModelStatus model_status) {
+  UMA_HISTOGRAM_ENUMERATION("Translate.Ranker.Model.Status", model_status,
+                            MODEL_STATUS_MAX);
+}
+
+}  // namespace
+
+const base::Feature kTranslateRankerQuery{"TranslateRankerQuery",
+                                          base::FEATURE_DISABLED_BY_DEFAULT};
+
+const base::Feature kTranslateRankerEnforcement{
+    "TranslateRankerEnforcement", base::FEATURE_DISABLED_BY_DEFAULT};
+
+const base::Feature kTranslateRankerLogging{"TranslateRankerLogging",
+                                            base::FEATURE_DISABLED_BY_DEFAULT};
+
+TranslateRanker::~TranslateRanker() {}
+
+// static
+bool TranslateRanker::IsEnabled() {
+  return IsQueryEnabled() || IsEnforcementEnabled();
+}
+
+// static
+bool TranslateRanker::IsLoggingEnabled() {
+  return base::FeatureList::IsEnabled(kTranslateRankerLogging);
+}
+
+// static
+bool TranslateRanker::IsQueryEnabled() {
+  return base::FeatureList::IsEnabled(kTranslateRankerQuery);
+}
+
+// static
+bool TranslateRanker::IsEnforcementEnabled() {
+  return base::FeatureList::IsEnabled(kTranslateRankerEnforcement);
+}
+
+// static
+TranslateRanker* TranslateRanker::GetInstance() {
+  return base::Singleton<TranslateRanker>::get();
+}
+
+std::unique_ptr<TranslateRanker> TranslateRanker::CreateForTesting(
+    const std::string& model_data) {
+  std::unique_ptr<TranslateRanker> ranker(new TranslateRanker());
+  CHECK(ranker != nullptr);
+  ranker->ParseModel(0, true, model_data);
+  CHECK(ranker->model_ != nullptr);
+  return ranker;
+}
+
+bool TranslateRanker::ShouldOfferTranslation(
+    const TranslatePrefs& translate_prefs,
+    const std::string& src_lang,
+    const std::string& dst_lang) {
+  // The ranker is a gate in the "show a translation prompt" flow. To retain
+  // the pre-existing functionality, it defaults to returning true in the
+  // absence of a model or if enforcement is disabled. As this is ranker is
+  // subsumed into a more general assist ranker, this default will go away
+  // (or become False).
+  const bool kDefaultResponse = true;
+
+  // If we don't have a model, request one and return the default.
+  if (model_ == nullptr) {
+    FetchModelData();
+    return kDefaultResponse;
+  }
+
+  DCHECK(model_->has_logistic_regression_model());
+  SCOPED_UMA_HISTOGRAM_TIMER("Translate.Ranker.Timer.ShouldOfferTranslation");
+
+  // TODO(rogerm): Remove ScopedTracker below once crbug.com/646711 is closed.
+  tracked_objects::ScopedTracker tracking_profile(
+      FROM_HERE_WITH_EXPLICIT_FUNCTION(
+          "646711 translate::TranslateRanker::ShouldOfferTranslation"));
+
+  const std::string& app_locale =
+      TranslateDownloadManager::GetInstance()->application_locale();
+  const std::string& country = translate_prefs.GetCountry();
+  int accept_count = translate_prefs.GetTranslationAcceptedCount(src_lang);
+  int decline_count = translate_prefs.GetTranslationDeniedCount(src_lang);
+  int ignore_count = translate_prefs.GetTranslationIgnoredCount(src_lang);
+  DVLOG(3) << "TranslateRanker: features=["
+           << "src_lang='" << src_lang << "', dst_lang='" << dst_lang
+           << "', country='" << country << "', locale='" << app_locale
+           << ", accept_count=" << accept_count
+           << ", decline_count=" << decline_count
+           << ", ignore_count=" << ignore_count << "]";
+
+  double score = CalculateScore(accept_count, decline_count, ignore_count,
+                                src_lang, dst_lang, app_locale, country);
+
+  DVLOG(2) << "TranslateRanker Score: " << score;
+
+  bool result = (score >= kTranslationOfferThreshold);
+
+  UMA_HISTOGRAM_BOOLEAN("Translate.Ranker.QueryResult", result);
+
+  return result;
+}
+
+TranslateRanker::TranslateRanker() {}
+
+double TranslateRanker::CalculateScore(int accept_count,
+                                       int decline_count,
+                                       int ignore_count,
+                                       const std::string& src_lang,
+                                       const std::string& dst_lang,
+                                       const std::string& locale,
+                                       const std::string& country) {
+  SCOPED_UMA_HISTOGRAM_TIMER("Translate.Ranker.Timer.CalculateScore");
+  DCHECK(model_ != nullptr);
+  DCHECK(model_->has_logistic_regression_model());
+
+  int total_count = accept_count + decline_count + ignore_count;
+  double accept_ratio =
+      (total_count == 0) ? 0.0 : (double(accept_count) / total_count);
+  double decline_ratio =
+      (total_count == 0) ? 0.0 : (double(decline_count) / total_count);
+  double ignore_ratio =
+      (total_count == 0) ? 0.0 : (double(ignore_count) / total_count);
+  DVLOG(3) << "TranslateRanker: ratios=["
+           << ", accept_ratio=" << accept_ratio
+           << ", decline_ratio=" << decline_ratio
+           << ", ignore_ratio=" << ignore_ratio << "]";
+
+  const chrome_intelligence::TranslateRankerModel::LogisticRegressionModel&
+      logit = model_->logistic_regression_model();
+  double dot_product =
+      (accept_ratio * logit.accept_ratio_weight()) +
+      (decline_ratio * logit.decline_ratio_weight()) +
+      (ignore_ratio * logit.ignore_ratio_weight()) +
+      (accept_count * logit.accept_count_weight()) +
+      (decline_count * logit.decline_count_weight()) +
+      (ignore_count * logit.ignore_count_weight()) +
+      ScoreComponent(logit.source_language_weight(), src_lang) +
+      ScoreComponent(logit.dest_language_weight(), dst_lang) +
+      ScoreComponent(logit.country_weight(), country) +
+      ScoreComponent(logit.locale_weight(), locale);
+  return Sigmoid(dot_product + logit.bias());
+}
+
+int TranslateRanker::GetModelVersion() const {
+  return (model_ == nullptr) ? 0 : model_->version();
+}
+
+void TranslateRanker::FetchModelData() {
+  // Exit if the model has already been successfully loaded.
+  if (model_ != nullptr) {
+    return;
+  }
+
+  // Exit if the download has been throttled.
+  if (base::Time::NowFromSystemTime() < next_earliest_download_time_) {
+    return;
+  }
+
+  // Create the model fetcher if it does not exist.
+  if (model_fetcher_ == nullptr) {
+    model_fetcher_.reset(new TranslateURLFetcher(kFetcherId));
+    model_fetcher_->set_max_retry_on_5xx(kMaxRetryOn5xx);
+  }
+
+  // If a request is already in flight, do not issue a new one.
+  if (model_fetcher_->state() == TranslateURLFetcher::REQUESTING) {
+    DVLOG(2) << "TranslateRanker: Download complete or in progress.";
+    return;
+  }
+
+  DVLOG(2) << "TranslateRanker: Downloading model...";
+
+  download_start_time_ = base::Time::Now();
+  bool result = model_fetcher_->Request(
+      GetTranslateRankerURL(),
+      base::Bind(&TranslateRanker::ParseModel, base::Unretained(this)));
+
+  if (!result) {
+    ReportModelStatus(MODEL_STATUS_DOWNLOAD_THROTTLED);
+    next_earliest_download_time_ =
+        base::Time::NowFromSystemTime() +
+        base::TimeDelta::FromMinutes(kDownloadRefractoryPeriodMin);
+  }
+}
+
+void TranslateRanker::ParseModel(int /* id */,
+                                 bool success,
+                                 const std::string& data) {
+  UMA_HISTOGRAM_MEDIUM_TIMES("Translate.Ranker.Timer.DownloadModel",
+                             base::Time::Now() - download_start_time_);
+
+  SCOPED_UMA_HISTOGRAM_TIMER("Translate.Ranker.Timer.ParseModel");
+
+  // We should not be here if the model has already been downloaded and parsed.
+  DCHECK(model_ == nullptr);
+
+  // On failure, we just abort. The TranslateRanker will retry on a subsequent
+  // translation opportunity. The TranslateURLFetcher enforces a limit for
+  // retried requests.
+  if (!success) {
+    ReportModelStatus(MODEL_STATUS_DOWNLOAD_FAILED);
+    return;
+  }
+
+  // Create a new model instance, parse and validate the data, and move it over
+  // to be used by the ranker.
+  std::unique_ptr<chrome_intelligence::TranslateRankerModel> new_model(
+      new chrome_intelligence::TranslateRankerModel());
+
+  bool is_parseable = new_model->ParseFromString(data);
+  if (!is_parseable) {
+    ReportModelStatus(MODEL_STATUS_PARSE_FAILED);
+    return;
+  }
+
+  bool is_valid = new_model->has_logistic_regression_model();
+  if (!is_valid) {
+    ReportModelStatus(MODEL_STATUS_VALIDATION_FAILED);
+    return;
+  }
+
+  ReportModelStatus(MODEL_STATUS_OK);
+  model_ = std::move(new_model);
+  model_fetcher_.reset();
+
+  DVLOG(3) << "Successfully loaded model version " << GetModelVersion() << ".";
+}
+
+void TranslateRanker::FlushTranslateEvents(
+    std::vector<metrics::TranslateEventProto>* translate_events) {
+  if (IsLoggingEnabled()) {
+    translate_events->swap(translate_events_cache_);
+    translate_events_cache_.clear();
+  }
+}
+
+void TranslateRanker::RecordTranslateEvent(
+    const metrics::TranslateEventProto& translate_event) {
+  if (IsLoggingEnabled())
+    translate_events_cache_.push_back(translate_event);
+}
+
+}  // namespace translate